This application claims the priority of German application 197 37 332.1, filed in Germany on Aug. 27, 1997, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a rotor cup for open-end spinning aggregates comprising a rough-surface fiber collecting groove relative to the fibers to be spun, the surface of which is provided with hard particles, and also comprising a smooth fiber sliding surface relative to the fibers, which is free of hard particles.
German published patent application 43 05 626 discloses that the fiber collecting groove has a greater friction resistance than the fiber sliding surface. This permits the fibers to slip sufficiently quickly into the fiber collecting groove and still take on the circumferential speed of the rotor at the latest at the fiber collecting groove. The surfaces of the rotor cup are entirely covered with a nickel-diamond plating. The desired roughness in the fiber collecting groove comes about in that individual diamond particles project out from the plating. The fiber sliding surface, in contrast, is subsequently smoothed in that a large proportion of the diamond grains are pulled out, whereby the fiber sliding surface loses the undesired grip effect.
The disadvantage is that first costly diamond particles are applied to the entire surface of the rotor cup, although they are only really required in the fiber collecting groove.
It is an object of the present invention to plate a rotor cup of the above mentioned type in such a way that from the very beginning, diamond particles are applied only where they are actually required.
This object has been achieved in accordance with the present invention in that the hard particles are rolled into the fiber collecting groove.
The hard particles are thus applied not by means of plating the surface of the rotor cup, but by mechanical means, whereby it is irrelevant whether the surface is plated or not. Much fewer hard particles are hereby needed in order that the rotor cup is adapted in the desired way to the spinning process.
Although in the case of the hard particles, corundum, quartz or other particles can be used, diamond grains are preferred. These are not only favorable for the spinning results, but are also favorable with regard to the wear of the fiber collecting groove. Favorable for yarn formation is a grain size of 3 to 4 .mu.m.
Although it is possible that, for example, emery grains can be rolled onto a steel surface and adhere well, it is especially advantageous when the fiber collecting groove is provided with a soft nickel plating before the grains are rolled in, according to certain preferred embodiments of the invention. For the purpose of the invention, in addition to the fiber collecting groove, the fiber sliding surface and if required the entire surface of the rotor cup is nickel-plated. This achieves on the one hand the desired smoothness of the fiber sliding surface and on the other hand an adequate protection against corrosion. The nickel plating is then hardened by means of heat treatment after the hard particles have been rolled in.
According to certain preferred embodiments, the fiber collecting groove is provided with a further nickel plating after the hard particles have been rolled in and after the hardening process. This further plating can be worn off during operation of the spinning rotor, so that the hard particles come to the surface. Remains of the second nickel plating remain in the spaces between the particles, so that these adhere better and are not so easily loosened from the surface.
It is favorable when the fiber sliding surface has a pitted surface. This can be applied according to certain preferred embodiments in that the hardened first nickel plating can be treated with a gritted roller. A second plating may be applied over the first plating, which second plating adapts to the gritted texture.
The preferred process for treating a rotor cup according to the present invention takes place in that firstly at least the fiber sliding surface and the fiber collecting groove are nickel-plated, in that subsequently hard particles are rolled into the nickel plating of the fiber collecting groove, and in that at least the fiber collecting groove is subsequently nickel-plated again and that the rotor cup is subsequently temper-hardened. The nickel plating, applied before the hard particles are rolled in, should be hardened after the hard particles have been rolled in.
For the purpose of preferred embodiments of the present invention, the fiber collecting groove is brushed over after the hard particles have been rolled in and before a possible subsequent nickel plating. Thus loose material is reliably removed, in particular before a second nickel plating may be applied.
The fiber sliding surface can be treated in the way of a pitted surface at the latest before a subsequent nickel plating. This can occur already on the steel surface. With the aid of such an orange peel structure, the so-called glass pane effect which occurs when the fibers are sliding down into the fiber collecting groove is prevented.
In practice, the fiber collecting groove is treated with a hard, rotating pressure disk after the hard particles to be rolled in have been filled in. The contour of the pressure disk must match the fiber collecting groove, and is designed blade-like with a very small radius. When the particles are being rolled in, very high specific pressures arise, without particular measures being necessary to create the required pressure. The pressure disk may be provided with a miniature tooth structure on its surface.
Other particles may possibly be added to the hard particles to be rolled in, which intensify the merging of the particles with the base.
When the hard particles are rolled in, the rotor cup should be supported from the outside. For this purpose, the outer contour of the rotor cup must have a sufficiently wide supporting surface in the form of a bearing surface.